Inferior anterolateral bilevel dissection of the skull base. The left side of the image presents the right side of the neck with profiles of the internal carotid artery and internal jugular vein adjacent to the lateral mass of the atlas. The vertebral artery fills its transverse foramen and the dens of the axis is seated behind its anterior arch. Immediately posterior to these is the spinal cord and anterior spinal artery with exposed anterior roots of the upper cervical spinal nerves. The left vertebral artery has ascended through the foramen magnum. The left portion of the occipital, temporal, and greater wing of sphenoid bones have been removed to expose the cerebellum, brainstem, sigmoid sinus, inferior petrosal sinus, internal carotid artery in the carotid canal, and the middle meningeal artery (enclosed by the roots of the auriculotemporal nerve) entering the foramen spinosum. Portions of the trigeminal, abducens, facial, vestibulocochlear nerves can be seen, as well as the labyrinthine artery, a branch of the anterior inferior cerebellar artery. The glossopharyngeal and vagus nerves are shown coursing toward the jugular foramen in company with the inferior petrosal sinus. (Image courtesy of AL Rhoton, Jr.)